Normally a “cracked” flex plate (flywheel) will produce more of a squeaking sound than a rattling noise - however that is quite possible.

Loose torque converter to flex plate bolts is another possibility.

In any event *hands-on* inspection will be required .. “Flexing” the flywheel using a prying tool will usually reveal cracking - trainer ear will recognize it straight away - as well as loose bolts to torque converter.